Fire retardant coating composition

Abstract

The claimed invention relates to a water-insoluble fire retardant coating composition and a method of rendering PVC cable fire resistant.

We claim: 
     
       1. A coating composition suitable for protecting cable against performance derating caused by thermal damage comprising about 71.3 to about 81.5% by weight of a sodium silicate/latex blend said blend comprising a mixture of about 52.0 to about 57.0% by weight of sodium silicate, about 6.4 to about 11.4% by weight of water, and about 34.0 to about 39.0% by weight of neoprene or polydimethylsiloxane latex, and about 18.5 to about 28.7% by weight of silica-containing powder consisting essentially of either ground perlite, fumed silica or mixtures thereof. 
     
     
       2. The fire retardant coating composition according to claim 1, wherein the silica-containing powder comprises about 32.0 to 100 percent by weight perlite and 0 to about 68.0 percent by weight fumed silica. 
     
     
       3. The fire retardant coating composition according to claim 1 wherein the silica-containing powder further comprises about 5.0 to about 16.4 percent by weight of the powder of china clay. 
     
     
       4. The fire retardant coating composition according to claim 1, wherein the silica-containing powder further comprises an additive selected from the group consisting of zinc oxide, titanium dioxide and mixtures thereof. 
     
     
       5. The fire retardant coating composition according to claim 4, wherein the additive comprises about 1.9 to about 9.0 percent by weight zinc oxide and about 4.6 to about 13.5 percent by weight titanium dioxide. 
     
     
       6. The fire retardant coating composition according to claim 1, wherein the silica-containing powder further comprises a mineral selected from the group consisting of quartz and volcanic rock. 
     
     
       7. The fire retardant coating composition according to claim 1, further comprising up to about an additional 12% by weight of sodium silicate/latex blend. 
     
     
       8. The coating composition according to claim 1, wherein the non-toxic latex is selected from the group consisting of noeprene. 
     
     
       9. The fire retardant coating composition according to claim 1, wherein the silica-containing powder comprises a compound selected from the group consisting of ground perlite, fumed silica, and mixtures thereof. 
     
     
       10. A method of rendering cable resistant to performance derating caused by thermal damage, which comprises: mixing about 18.5 to about 28.7% by weight of a silica-containing powder consisting essentially of either ground perlite, fumed silica or mixtures thereof into a sodium silicate latex blend comprising about 52.0 to about 57.0% by weight sodium silicate, about 34.0 to about 39.0% by weight of a neoprene or polydimethylsiloxane emulsion, and about 6.4 to 11.4% by weight water; and   applying at least one layer of the mixture to the cable, wherein the thickness of the mixture is controlled by the amount of said silica-containing powder used.   
     
     
       11. The method according to claim 10, wherein two layers of mixture are applied to the cable and the first layer is thinner than the second layer. 
     
     
       12. The method according to claim 10, wherein about 71.3 to about 81.5 percent by weight of sodium silicate/latex blend and about 18.5 to about 28.7 percent by weight of silica-containing powder are mixed. 
     
     
       13. The method according to claim 10, wherein the silica-containing powder comprises a compound selected from the group consisting of ground perlite, fumed silica, and mixtures thereof. 
     
     
       14. The method according to claim 13, wherein the silica-containing powder comprises about 32.0 to 100 percent by weight perlite and 0 to about 68.0 percent by weight fumed silica. 
     
     
       15. The method according to claim 10, wherein the silica-containing powder contains about 5.0 to about 16.4 percent by weight of the powder of china clay. 
     
     
       16. The method according to claim 10, further comprising adding an additive selected from the group consisting of zinc oxide, titanium dioxide and mixtures thereof to the mixture. 
     
     
       17. The method according to claim 10, wherein the silica-containing powder includes a mineral selected from the group consisting of quartz and volcanic rock. 
     
     
       18. The method according to claim 10, wherein the cable is polyvinylchloride cable. 
     
     
       19. The method according to claim 10, wherein the latex emulsion is selected from the group consisting of neoprene.